How does immunisation work?

Find out how your immune system works, and vaccines strengthen it.

How your immune system works

Every day you come into contact with germs, including bacteria and viruses. A healthy immune system stops you getting sick from these germs.

The immune response is the way your body defends itself. It recognises harmful bacteria, viruses and any other substances, also known as antigens, when they enter your body.

When an antigen like the cold virus enters your body, your immune response first produces something called mucus. The mucus tries to flush out the virus and stop more of it from entering the body.

Next, your immune response can send white blood cells to surround the virus to prevent more harm.

Lastly, it can produce special proteins called antibodies. Antibodies can lock onto and destroy the virus.

The immune system is at work all the time to keep us as healthy as possible.

Vaccines strengthen your immune system

Vaccines are a safe and clever way of producing an immune response in the body without causing illness.

Vaccines use dead or severely weakened viruses to trick our bodies into thinking we have already had the disease.

When you get a vaccine, your immune system responds to these weakened ‘invaders’ and creates antibodies to protect you against future infection. It has special ‘memory’ cells that remember and recognise specific germs or viruses.

Vaccines strengthen your immune system by training it to recognise and fight against specific germs.

When you come across that virus in the future, your immune system rapidly produces antibodies to destroy it. In some cases, you may still get a less serious form of the illness, but you are protected from the most dangerous effects.

Is 'natural' immunisation better?

If a disease infects you, then you may become immune to it in the future. We call this 'natural' immunity.

Some people believe that natural immunity is better than the immunity from vaccines. But the risks associated with natural immunity are much higher than risks associated with immunity provided by vaccines. Some highly contagious diseases can lead to severe complications. They can make you very ill or even be fatal.

The benefits of vaccination far outweigh the risks. Vaccination protects you and your family from diseases, including ones that are deadly. It also protects other people in your community, including people who are vulnerable, too young, or too sick to be immunised.

The estimation is that worldwide immunisation programs prevent about 2.5 million deaths every year.

Vaccination also helps protect the health of future generations, for example against the crippling disease polio.

Find out more 

How do vaccines affect immunity? fact sheet

Fact sheet about how vaccines affect and strengthen natural immunity, how vaccines work and why vaccines are given to babies.

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